A game theoretic approach for delay minimization in slotted ALOHA

Analysis of Networked Event-Based Control with a Shared Communication Medium: Part II – Slotted ALOHA

Slotted Aloha provides a simple way for accommodating the massive access of Machine-to-Machine (M2M) communications. Yet, the delay performance of slotted Aloha has long been observed to significantly deteriorate as the network size grows. It is therefore important to study how to optimize the delay performance of slotted Aloha in a large-scale network. This paper focuses on the optimization of access delay of a buffered slotted Aloha network, where n nodes transmit to a common receiver in fading channels. Specifically, by deriving the closed-form expressions of the network steady-state points in both unsaturated and saturated conditions, the first and second moments of access delay of each packet are obtained as explicit functions of system parameters, and minimized by optimizing the transmission probability of each node. The analysis shows that to achieve the minimum mean access delay, the transmission probability of each node should be reduced as the network size increases, leading to a diminishing node data rate unless the information encoding rate is jointly optimized. The minimum mean access delay for a given data rate requirement is further characterized, and effects of key parameters such as the minimum required data rate for each node, the mean received signal-to-noise ratio of each packet and the number of nodes on the rate-constrained minimum mean access delay are discussed. The practical insights of the analysis are also demonstrated by taking the example of an LTE-M system with smart grid applications.

We present a comprehensive steady-state analysis of threshold-ALOHA, a distributed age-aware modification of slotted ALOHA proposed in recent literature. In threshold-ALOHA, each terminal suspends its transmissions until the Age of Information (AoI) of the status update flow it is sending reaches a certain threshold Γ. Once the age exceeds Γ, the terminal attempts transmission with constant probability τ in each slot, as in standard slotted ALOHA. We analyze the time-average expected AoI attained by this policy, and explore its scaling with network size, n. We derive the probability distribution of the number of active users at steady state, and show that as network size increases the policy converges to one that runs slotted ALOHA with fewer sources: on average about one fifth of the users is active at any time. We obtain an expression for steady-state expected AoI and use this to optimize the parameters Γ and τ, resolving the conjectures in previous literature by confirming that the optimal age threshold and transmission probability are 2.2n and 4.69/n, respectively. We find that the optimal AoI scales with the network size as 1.4169n, which is almost half the minimum AoI achievable with slotted ALOHA, while the loss from the maximum throughput of e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> remains below 1%. We compare the performance of this rudimentary algorithm to that of the SAT policy [2] that dynamically adapts its transmission probabilities.

In this paper, we propose the effective analysis methodology to be applied to the monitoring network of synchronous under the IEEE 802.15.4 standard, we call it real-time wireless sensor network (RT-WSN) in this network that is build for the “real-time” specific application. We aim at the slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) of algorithm of channel access mechanism in IEEE 802.15.4 MAC layer to build the network model and analyze the average packet delay over RT-WSN based on probability theory. The proposed theoretical analysis was nearly consistent with the correct result of simulation and the experiment. The result shows that this slotted CSMA/CA cannot be effectively applied to RT-WSN since it cannot avoid the high packet collision in the saturation throughput conditions. When receiving 10 sensor nodes, the packet delay caused by packet collision is 6.29 times more than one ideal model. Hence, we propose the like Time Division Multiple Access (TDMA) to improve CSMA/CA in packet collision problem. With neighbor table, TDMA can record the network states and implement the dynamic network configuration. Our experimental results show that TDMA can own the characteristics of the stable and limited packet delay. Once the total traffic load is lower than maximum throughput, it can guarantee the packet transmission of real-time without considering the amount of sensor nodes in network. Moreover, compare with CSMA/CA in 10 sensor nodes conditions, 57 % of the maximum throughput is improved. Therefore, we can meet with the QoS requirement of packet delay in RT-WSN. In the end, we install a remote ECG monitoring system for an example of application situation in the sanatorium. We provide steady wireless transmission media for the front of this system and reach the purpose of real-time remote medical care.

Markov chain analysis of collaborative codes in random multi access communication systems

Multiple packet reception (MPR) is becoming a viable reality for wireless random access protocols thanks to advances in the physical layer and new coding techniques. In the simplest $K$ -MPR model, a receiver can resolve up to $K\geq 1$ parallel transmissions. We extend the classical analysis of pure and slotted ALOHA to $K$ -MPR devices with arbitrary degree $K$ for fixed and variable packet size. Through a parsimonious modeling approach, we derive relatively simple analytical expressions. In this way, we gain insight and quantitative understanding on the fundamental tradeoffs between pure and slotted ALOHA and on the scaling of maximum achievable throughput with $K$ .

The effect of multipath interference on the performance of packet radios is investigated. The protocols considered include pure ALOHA and slotted ALOHA. Signal reception with and without capture effect is considered in this analysis. Mathematical expressions of system throughput and packet delay have been successfully obtained for each protocol. Numerical calculations are used to demonstrate when the multipath interference can be ignored and when it can be disastrous. >

The key contributions of this paper are the proposed Pure Collective Aloha (PCA) medium access control (MAC) protocol with multilevel powers and its closed-form theoretical analysis. The PCA MAC protocol collects a batch of packets before transmitting these packets sequentially in the channel. The key idea in the design of this PCA MAC protocol with multilevel powers is to spread out the arrivals of each batch of packets in a channel and the multilevel powers of the packets received at the receiver allow capture for the case of the strongest signal power packet among the overlapping lower signal power packets to be successfully received at the receiver. If it is the only received packet, it is successfully received, regardless of its received power level. The PCA MAC protocol with multilevel powers is analyzed theoretically. The explicit closed-form expressions for the optimal offered loads and the maximum throughputs of the Pure Aloha, the Slotted Aloha and the PCA MAC protocols with multilevel powers are presented. The numerical results show that the throughput of the asynchronous PCA MAC protocol with multilevel powers is about 90.5% better than that of the asynchronous Pure Aloha MAC protocol with multilevel powers and can approach the maximum throughput bound of the synchronous Slotted Aloha MAC protocol with multilevel powers, without the need of any synchronization mechanism to slot boundaries.

This paper deals with two representative unbalanced traffic cases for two-hop wireless relay access systems employing network coding and a slotted ALOHA protocol. Network coding is a recent and highly regarded technology for capacity enhancement with multiple unicast and multisource multicast networks. We have analyzed the performance of network coding on a two-hop wireless relay access system employing the slotted ALOHA under a balanced bidirectional traffic. The relay nodes will generally undergo this unbalanced multidirectional traffic but the impact of this unbalanced traffic on network coding has not been analyzed. This paper provides closed-form expressions for the throughput and packet delay for two-hop unbalanced bidirectional traffic cases both with and without network coding even if the buffers on nodes are unsaturated. The analytical results are mainly derived by solving queueing systems for the buffer behavior at the relay node. The results show that the transmission probability of the relay node is a design parameter that is crucial to maximizing the achievable throughput of wireless network coding in slotted ALOHA on two-hop unbalanced traffic cases. Furthermore, we show that the throughput is enhanced even if the traffic at the relay node is unbalanced.

In this paper, we propose a distributed contention resolution algorithm for multi-packet reception slotted ALOHA systems, which is based on backlog estimation. In the algorithm, a base station broadcasts a binary-valued collision indicator and the identifications of the packets successfully received, when some of packets simultaneously transmitted collide. Then, mobile terminals (MTs) estimate the expected number of MTs involved in the collision given the number of packets successfully transmitted and the collision indicator. Based on this estimation, MTs construct the backlog information and choose their retransmission probability in order to maximize the system throughput. In simulations, the proposed algorithm shows 67% throughput efficiency against the maximum achievable system throughput. The stability of the algorithm is evaluated by examining negative drift from simulation.

The dynamic queue MAC protocol is designed explicitly for networks with multipacket reception (MPR). It provides efficient channel utilization with a simple on-line implementation. In this paper, we present an analysis of the steady-state performance of the dynamic queue protocol. Its throughput and normalized throughput in CDMA networks are studied and compared to that of the optimal MAC and the slotted ALOHA with optimal retransmission probability.

Performance evaluation of framed slotted ALOHA with reservation packets and succesive interference cancelation for M2M networks

Network coding has shown the promise of significant throughput improvement. In this paper, we study the network throughput using network coding and explore how the maximum throughput can be achieved in a two-way relay wireless network. Unlike previous studies, we consider a more general network with arbitrary structure of overhearing status between receivers and transmitters. To efficiently utilize the coding opportunities, we invent the concept of network coding cliques (NCCs), upon which a formal analysis on the network throughput using network coding is elaborated. In particular, we derive the closed-form expression of the network throughput under certain traffic load in a slotted ALOHA network with basic medium access control. Furthermore, the maximum throughput as well as optimal medium access probability at each node is studied under various network settings. Our theoretical findings have been validated by simulation as well. © 2014 IEEE.

The throughput characteristics of contention-based random-access systems (RAS's) which use <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -ary tree algorithms (where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q \geq 2</tex> is the number of groups into which contending users are split) of the Capetanakis-Tsybakov-Mikhailov-Vvedenskaya type are analyzed for an infinite population of identical users generating packets according to a Poisson process. Both free and blocked channel-access protocols are considered in combination with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -ary collision resolution algorithms that exploit either binary ("collision/no collision") or ternary ("collision/ success / idle") feedback. For the resulting RAS's, functional equations for transformed generating functions of the first two moments of the collision resolution interval length are obtained and solved. The maximum stable throughput as a function of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> is given. The results of a packet-delay analysis are also given, and the analyzed RAS's are compared among themselves and with the slotted ALOHA system in terms of both system throughput and packet delay. It is concluded that the "practical optimum" RAS (in terms of ease of implementation combined with good performance) uses free (i.e., immediate) channel access and ternary splitting (i.e., <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q = 3</tex> ) with binary feedback.

For slotted random access systems, the slotted ALOHA protocol provides the maximum throughput of 0.368 (packets/slot) while in the category of splitting (or tree) algorithms, the maximum achievable throughput can reach up to 0.487 with the first-come first-serve (FCFS) algorithm. It has been so far demonstrated that the FCFS algorithm can achieve this maximum throughput only for Poisson traffic. This may limit its application in practical systems, where packet arrivals may not be Poissonian. In this paper, we propose a novel online transmission control framework that introduces random splitting upon collisions and controls the transmission probabilities optimally at each slot by estimating the number of active users in the system. The proposed algorithm is said to be online as it estimates the number of active users slot by slot recursively, and thus can adapt to network dynamics. We first show that the splitting algorithm of our interest can achieve the throughput of 0.532 if the number of users involved in a collision could be known, which serves as a guideline for the upper limit for the random access systems with splitting. Then, when the information on the number of collided users is not available, we show that the proposed algorithm can achieve the maximum throughput of 0.487 for Poisson arrivals while achieving shorter access delay than FCFS. When more bursty traffic than Poisson process is applied, the proposed algorithm shows much better throughput and delay performance than FCFS.